There has been considerable interest in high quality nitride films because of their important properties and applications in semiconductor, electronic and optoelectronic industry. For example, titanium nitride (TiN) exhibits high hardness, high chemical and thermal stability, low electrical resistivity, and excellent adhesion to substrates, that make TiN the most popular and widely studied material in the semiconductor industry. Aluminum nitride (AlN0 has a wide band-gap of 6.2 eV, high thermal conductivity, strong piezoelectricity and good thermal stability, which makes it suitable as a substrate for UV detectors and blue emitting LEDs. Titanium-aluminum-nitride (Ti1−xAlxN) composites may take advantage of properties of both TiN and AlN, such as they have a high melting point, chemical inertness, superior oxidation resistance and good thermodynamic stability. Because of these properties, they are excellent candidates for use as optical coatings in industry, diffusion barriers in microelectronics, electrodes in micro-electro-mechanical devices, and hard wear-resistant coatings in machining applications.
Nitride materials such as titanium nitride (TiN), aluminum nitride (AlN), and gallium nitride (GaN) can be deposited in the form of films by physical vapor depositions such as magnetron sputtering, ion beam sputtering, ion beam assisted deposition (IBAD), arc evaporation, electron-beam (e-beam) evaporation, atomic layer deposition, thermal evaporation, molecular beam epitaxy (MBE) and pulsed laser deposition (PLD). Chemical vapor depositions such as plasma-enhanced chemical vapor deposition (PECVD), low-pressure chemical vapor deposition (LPCVD), and metalorganic chemical vapor deposition (MOCVD) have also been used. However, these deposition techniques have their limitations due to the cost of equipment, the ability to coat only flat surfaces, and the ability to coat only surfaces of limited size.
Chemical solution deposition techniques have been generally viewed as less capital intensive (see, Lange, “Chemical Solution Routes to Single-Crystal Thin Films”, Science, vol. 273, pp. 903-909, 1996 and Schwartz, “Chemical Solution Deposition of Perovskite Thin Films”, Chemical Materials, vol. 9, pp. 2325-2340, 1997). Also, chemical solution techniques are not generally limited to flat surfaces.
U.S. Pat. No. 6,589,457 by Li et al. is directed to deposition of metal oxides from aqueous solutions of water-soluble metal precursors and water-soluble polymers. While none of the examples included a polymer other than polyvinyl alcohol, Li et al. illustrate the continuing efforts in the development of chemical solution deposition processes.